CA1111977A

CA1111977A - Coating composition

Info

Publication number: CA1111977A
Application number: CA325,701A
Authority: CA
Inventors: Don H. Rotenberg; Patricia M. Cuffe; Bernard L. Laurin; Peter R. Ramirez
Original assignee: American Optical Corp
Current assignee: American Optical Corp
Priority date: 1978-04-18
Filing date: 1979-04-18
Publication date: 1981-11-03
Also published as: NL7902845A; AU520162B2; FR2423521B1; FR2423521A1; AU4598379A; DE2915066A1; GB2025444B; CH644619A5; JPS54139940A; GB2025444A

Abstract

Abstract of the Disclosure A coating composition which results from hydrolyzing 35 to 70 weight per cent tetraethyl orthosilicate and 60 to 20 weight per cent of certain silane is useful for providing abrasion resisting coatings for plastics after curing.
Optionally, up to 20 weight percent of a silane having a reactive polar site or, in the alternative, a small percentage of a surfactant may be used to provide a dyeable coated article.

Description

B~cJ~round of the Invention This invention relates to Si containing coating co.?esitions and more particularly to coatin~ compositions for polymeric substrates.
Prior Art U. S. Patent No. 3,894,881 issued ~uly 15, 1975 to . Suzuki et al. This patent reiates to a c02ting.composition which comprises a mixture of separately hydrolyzed Si contai~ing.:
- materîals and a metal salt. The patent does not refer to 10 any coating co~positions of a similar type which are hydrolyze~ -as a mixture.
Summary of the Invention We have developed an improved type of abrasion-resista~t coating based upon siloxane copolymers. These coa.ings are useful for increasing the abrasion resis,ance of plastics, especially those used for the manufacture of eyeglass lenses, sunglasses, goggles, ana windo~ and architec~ura glazing. Typical plastic substrates that can be used for these applications are polycarbonate, polymethyl me.hacrylate, 20 cellulose propionate, celluiose butyrate, and polydiethylene I ~lycol bis-allyl carbonate. Polyc2rbon2te and pol~diethylene ~.:
: glycol bis-aliyl carbonate are pre erred lens materials.
.: ~enses can be formed from thermoplastics by molding .
: . techniques, from thermosetting plastics by casting techniques, and from both by machining and surfacing processes. Such . .` lenses can be coated with the poiysiloxane coating to provide - a surface that is more xesistant-to both abrasion and solvent attack than the uncoated plastic.
.,' . ~.

,~ : , . . ~F . , - . . .. . . : -.

While these coatings provide good resistance to bo.h abrasion and solvents, they introduce an additional feature that was not possible before with earlier polysiloxane coatings. The polysiloxane coatings of this invention can be tinted or dyed with organic dyes so that coated lenses can be provided with fashion or sunglass colors in a manner simllar to the way uncoated lenses are now currently dyed in the industry.
The principal monomers of our copolymer three dimensional siloxane coating are tetraethyl orthosilica~e and certain combina,ions of methyltrimethoxy silane, methyltrietnoxysil~ne, ethyltrimethoxysilane, ethyltriethoxysilane, dimethyl-dimethoxysilane and dimethyldiethoxysilane. ~or example, useful abrasion resistant coatings for both polycarbonate and diethylene glycol bis-ally carbonate are prepared by reacting 40 to 70 weight per cent tetraethyl orthosilicate and 60 to 20 weight per cent of methyltrimethoxysilane to form~a highly-crosslinked polysiloxane network polymer. ~y .
allowing these monomers to hydrolyze in-si~u by addition of water to the alcohol solution, the polymer will form a tough abrasion -esistant coating when applied to the surface of a lens and then allowed to crosslink and cure by the application of heat either in the presence or absence of a catalyst.

: ~, ) : ' .
~ .
-~3~
' ~ :

,. . . . , - ~ .
: . . :

7 ~

When the substrate to be coated is one which will absorb water under humid conditions, e.g. poly diethylene glycol Bis (allyl carbonate) and cellulose acetate propionate, less tetraethyl orthosilicate is preferred. Suitable coatings for these substrates are obtained from the reaction of about 35 to 45 weight per cent tetraethyl orthosilicate, about 45 to 55 weight per cent methyltrimethoxy silane and about 5 to 15 weight per cent 3-glycidoxypropyltrimethoxy-silane.
10In addition to the discovery of these new abrasion resistant coatings, we have also discovered how to render them suitable for dyeing once they have been applied to and .
cured upon the surface of a lens. Since highly crosslinked !

. . .

:' ~ -3a-"' .

poiysiloxanes are rather impervious to attack by most coloring agents, we have developed two techniques to modify their properties so that organic dyes will penetrate the co2ting an~ will ~e adsorbed within the molecular structure.
;The first technique involves the addition of certain surfactants or wetting agents to the coating formulation.
For example, the addition of a non-ionic wetting agent such as Triton X-100, a polyethylene oxide derivative of nonylphenol made by Rohm & Haas Company, permits conventional ophthalmic organic dyes to penetrate into the coating. Another useful wetting agent is Fluorad FC-430, a non-ionic fluorinated alkyl ester made by the 3M Company. Coatings prepared with this material also permitted organic dyes to penetrate into the co~ting.
A second approach is the use of up to 20 weight per cent of a reactive siloxane monomers with polar sites that ; serves to attract the organic dyes. Typical reactive siloxane monomers are:
3-chloropropyltrimethoxysilane 3-glycidylpropyltrimethoxysilane 3-methacryloxypropyltrimethoxysilane bis~2-hydroxyethyl)aminoprop~ltrimethoxysilane and (3,4-epoxycyclohexyl)ethyl,rimethoxysilane These monomers are reacted with the basic tetraethyl orthos-; ilicate~silane coating formulation as shown in the examples to yield dyeable lens coatings. ~hen these monomers are used and if they are considered as part of the "silane"
component of the basic tetraetyyl orthosilicate/ silane mixture, the silane component must be present in a to~al of at least 30 weight per cent.

, , 7 ~

Example 1 2G8 grams of te,raethyl orthosilicate, 136 grams o~
methyltrimethoxysilane were hydrolyzed in 95 grams of alcohol (50% isopropanol, 50% n-butanol), 130 grams of water, 30 grams of acetic acid, and 14 drops of hydrochloric acid using an ice bath for 10 minutes to control the iniiial exotherm, and then at room temperature overnight.
Polycarbonate lenses were primed by dipping for one minute in a solution containing 10~ gamma-amino propyl triethoxysilane, 85% ethyl alcohol and 5% water, rinsed, air dried and then dip-coated in the abrasion-resistant coating solution and cured at 104 C for 8 hours. The resulting coatings were on the average of 2 microns thick and resistant to abrasion and solvent attack.
- Example 2 50 grams of methyltrimethoxysilane, 50 grams of tetraethyl ~ -orthosilicate, were hydrolyzed in 4~ grams of 50/S0 weight %
solution of isopropanol and n-butanol by stirring constantly while 35 grams Gf water and 10 grams of acetic acid were added dropwise. The solution was aged for 1 day.
Polycarbonate (primed as in Example 1) and CR-39 ~hydrolized) lenses were dip-coated with the abrasion-resistant coating solution and cured at 104C for 8 hours. The resu~ting coatings were on the average 2 microns thick and quite reslstant to abrasion and solvent attaok.

.
.

. .

' ,,, , ' ~ . -, .
- :, -, 7 ~
Example 3 100 grams of methyltrimethoxysilane, 100 grams o' tetraethyl orthosilicate, and 80 grams of 50/50 isopropanol-n-butanol were mixed while 70 grams of water and 20 grams of acetic acid,were 510wly added.
After aging the solution overnight, it was di~-ided into seven 50 gram batches to which 0, 0.1, 0.25, 0.50, 1.00,

2.50, and 5.00~ Triton X-100 was added, respectively.
Primed polycarbonate lenses were coated from each solution and cured at 220 F for 8 hours. The resulting coatings were 2-3 microns in thickness. They were dyed by dipping organic dye (ophthalmic grey from Brain Power Inc.) mixed with water. Visual transmission of the lenses after 5 minutes of dyeing at 200 F were 87~, 88~, 88~, 86%, 84~, 62%
and 25%, respectively.
Example 4 To 50 grams of coating solution as prepared in Example

3 above, was added 2~ ~luorad FC-430. Brimed polycarbona~e lenses were coated and cured as above. The coating again accepted the organic dye to give a visual transmission of 56% after 5 minutes of 200 F in the water dye mixture.
_ ample 5 24 grams of tetraethyl orthosilicate, 12 grams of methyltrimethoxysiland, 4 grams of 3-methacryloxypropyl-trimethoxysilane, were hydrolyzed in 19 grams of 50J50 isopropanol-n-butanol by slowly ,adding 1~.5 grams of water and 3.75 grams of acetic acid. The solution was aged three days.

:~LP~ 7 Primed polycarbonate lenses were coated and cured as in previou~ examples. The coating was receptive to convention ophthalmic organic dyes. Visual transmission equaled 7~%
aft..er 5 minutes at 200F in theaqueous/dye (BPI Grey) mixture.
Exa~lple 6 .24 grams of tetraethyl orthosilicate, 12 grams of - methyltrime,hoxysilane, and 6.~5 grams of bis(2-hydroxyethyl) aminopropyltriethoxysilane, were hydrolyzed in 16 grams of 50/50 alcohol by adding 12.75 grams of water and 3.75 grams of acetic acid slowly. The p~ was the adjusted , .
to 3 with hydrochloric acid.
Coated ~olycarbonate lenses again were quite receptive to the 5 minute dye treatment at 200F in the a~ueous mixture of BPI Grey. The lenses had a transmission of 74~.
Example 7 . 344 grams of tetratheyl orthosilicate, 430 grams of meth,yl-: trimethoxysilane and 86 grams of 3-glycidoxypropyl-trimethoxy-. silane were hydrolized by slowly adding 310 grams of a 50/50 ~.
. ' mixture of isopropyl alcohol and butyl alcohol, 310 grams of water and 69 grams of acetic acid at a rate that permitted the ' r,eaction to proceed without exceeding 30C. The coating solution '.~ should be aged about 4 days before use and has useful pot life of approximately 4 to 6.weeks.
~ Hydrolized CR-39 ophthalmic lenses were coated by dipping in ', ~ r ,: th,e aged coating solution and withdrawing them from the solution .,, . at à rate of about 10 inches per minute. The coating obtained wa5 about 2 to 3 microns thick - had good adhesion to the.lenses -' passed cycle humidity, boiling water and abrasion tests as well a~ enhanced the impact re9istance of the lenses.

7_ :
.

.. -. . . . . . . . . .. - -

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A coating composition which is curable to provide an optically clear abrasion resistant coating, which comprises a hydrolysis product of about 35 to 70 weight per cent tetraethyl orthosilicate and 60 to 20 weight per cent of a silane selected from the group consisting of methyl-trimethoxysilane, methyltrietheoxysilane, ethyltrimethoxy-silane, ethyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane and mixtures thereof and up to 20 weight per cent of a siloxane having a reactive polar site.

2. The coating composition according to claim 1 wherein about 60 weight per cent tetraethyl orthosilicate and about 40 weight per cent methyltrimethoxysilane.were hydrolyzed with a mixture of water, alcohol and acetic acid and then aged.

3. The coating composition according to claim 1 wherein about 50 weight per cent tetraethyl orthosilicate and 50 weight per cent methyltrimethoxysilane were hvdrolyzed with a mixture of water, alcohol and acetic acid and then aged.

4. The coating composition according to claim 1 further including at least 1.0 weight per cent of a non-ionic surf actant.

5. The coating composition according to claim 4 wherein the surfactant is selected from the group consisting of Triton X?100 and Fluorad FC?430.

6. The coating composition according to claim 1 wherein the silane having the reactive polar site is selected from the group consisting of 3-chloropropyltrimethoxysilane, 3-glycidylpropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, bis(2-hydroxyethyl)aminopropyltrimethoxysilane, and (3,4-epoxycyclohexyl)ethyltrimethoxysilane.

7. The coating composition according to claim 1 wherein about 60 weight per cent tetraethyl orothosilicate, 30 weight per cent methyltrimethoxysilane and 10 weight per cent 3-methacryloxypropyltrimethoxysilzne were hydrolyzed with a mixture of water, alcohol and acetic acid and then aged.

8. The coating composition according to claim 1 wherein about 57 weight per cent tetraethyl orthosilicate, about 28 weight per cent methyltrimethoxysilane and about 15 weight per cent bis(2-hydroxyethyl)aminopropyltriethoxysilane were hydrolyzed with a mixture of water, alcohol and acetic acid and then aged.

9. A coating composition which is curable to pro-vide an optically clear abrasion resistant coating, which comprises an hydrolysis product of about 35 to 45 weight per cent tetraethyl orthosilicate and 55 to 45 weight per cent methyltrimethoxysilane, and 5 to 15 weight per cent 3-glycidoxypropyltrimethoxysilane.

10. The coating composition according to Claim 1 wherein about 40 weight per cent tetraethyl orthosilicate and about 50 weight per cent methyltrimethoxysilane and 10 weight percent 3-glycidoxypropyltrimethoxysilane were hydrolized with a mixture of water, alcohol and acetic acid and then aged.

11. An ophthalmic lens coated with the composition of Claim 1.